node_limit 6.x-0.3

#429156: Show error message if limit is reached, #429224: Coding/Documentation guidelines, #429260: Remove rules on user/node type deletion by jcmarco, stBorchert: Coder cleanup, minor features and bug fixes.
Added node_limit_interval submodule - limits can now be applied within the past [time interval] (ex: 1 day, 37 weeks, etc)